1. Field of Invention
The present invention relates to a backlight module, and more particularly to a backlight module which can reduce manufacturing cost.
2. Description of Related Art
With advancements in semiconductor industry and relevant electronic industries, digital devices such as mobile phones, digital cameras, digital video cameras, notebooks, and desktop computers have made progress to meet requirements for easy operation, multiple functionality, and attractive exterior design. However, using IT products as described above demands a suitable display screen acting as a man-machine interface, and the display screens of the products aforementioned facilitate various operations. Recently, liquid crystal displays (LCDs) have become a main stream of the display screens. However, the LCD is not self-luminescent, so that a backlight module must be employed and placed under the LCD to serve as a light source so as to make display possible. FIG. 1 illustrates a schematic cross-sectional view of a conventional backlight module. Referring to FIG. 1, a side type backlight module 100 includes a back plate 110, a frame 120, a light guide plate 130, and a light source 140. The frame 120 is leaned against the back plate 110 and the light guide plate 130 is disposed on the back plate 110. The light source 140 is disposed on a side of the back plate 110 and located by a light incident surface 132 of the light guide plate 130. A light emitted by the light source 140 enters the light guide plate 130, where a light path thereof is corrected and then the light emitted by the light source 140 is emitted.
Generally, the light source 140 incorporated in the backlight module 100 is mostly cold cathode fluorescence lamp (CCFL). In recent years, as the light emitting efficiency of light-emitting diode (LED) has continuously increased, the LED has gradually replaced the CCFL as the light source 140 of the backlight module 100. Compared with the CCFL, the LED has absolute advantages. For example, an LED is physically compact, long lasting, low voltage/current driven, durable, mercury free (pollution free), and with high emission efficiency (power saving), etc. FIG. 2A is a schematic diagram of using conventional LEDs as the light source. Referring to FIG. 2A, generally, each of LEDs 142 is a package structure, the LED 142 is thus disposed on a flexible substrate 144 to be manufactured into a light bar and then adopted as the light source 140 of the backlight module 100.
Referring to FIG. 1 and FIG. 2A simultaneously, since gaps are present between the LEDs 142 and the light incident surface 132 of the light guide plate 130, lights with large emitting angles are leaked through the gaps, such that the LCD has partial hot spots affecting a display effect of the LCD as illustrated in a schematic top view of the backlight module having partial hot spots in FIG. 2B. When viewing the backlight module 100 of FIG. 1 from the top, some of elements such as a reflector 150, the back plate 110, and the frame 120 canopy the light source 140 in the diagram. Therefore, the reflector 150, the back plate 110, and the frame 120 are omitted in FIG. 2B.
Referring to FIG. 1, in a conventional method for solving the problem of partial hot spots, an upper reflector 150 is disposed between the light guide plate 130 and a top portion of the back plate 110 located on the light guide plate 130. Although the disposition of the upper reflector 150 prevents the problem of partial hot spots caused by the light emitted from the gap between the LED 142 and the light incident surface 132 of the light guide plate 130, a double-sided tape is required to adherently fix the reflector 150 to the back plate 110. Hence, a material cost of the double-sided tape and a manual assembling time have to be consumed.